1. Field
Methods and apparatuses consistent with the exemplary embodiments relate to an image scanning apparatus and paper transfer method of the image scanning apparatus, and more particularly, to an image scanning apparatus using a Brushless DC (BLDC) monitor for transferring paper, and a paper transfer method of the image scanning apparatus thereof.
2. Description of the Related Art
An image scanning apparatus is an apparatus which scans an original image of a document, picture or film, and converts the scanned image into digital data. In this case, the digital data can be displayed on a monitor of a computer or printed by a printer and generated then as an output image. Examples of such an image scanning apparatus are a scanner, copier, facsimile, and multi function peripheral (MFP) which embodies these functions in one apparatus.
In such an image scanning apparatus, numerous motors are used to perform various functions such as transferring printing paper or supplying printing paper. Recently, as it is possible to attach option units which perform various functions to an image scanning apparatus, the number of motors that can be used in an image scanning apparatus is increasing.
It is a recent trend to use a BLDC motor in an image scanning apparatus in order to prevent noise from occurring when driving the image scanning apparatus. A BLDC motor is a brushless motor that performs rectification electronically, and thus since a mechanical rubber is removed from between a brush and a rectifier, the motor has higher speed and less noise.
As aforementioned, a BLDC motor doesn't have a brush structure. Therefore, in the sense that it is necessary to sense location information of a rotator using a Hall sensor and to approve power on each phase of the BLDC motor in consecutive order and control the approved power, a driving circuit is used.
The conventional method was to control the BLDC motor using an analogue Phase-Locked Loop (PLL) type driving circuit.
However, it is difficult to apply such an analogue PLL type BLDC motor to an image scanning apparatus. The most important thing in a motor used in an image scanning apparatus is not only speed but also whether or not the speed is maintained constant in various speed bands that can cover expansion/reduction. However, in an analogue PLL type BLDC motor, a gain value of a driving circuit for maintaining a constant speed is fixed to an external device using resistance and capacitor, and once the gain value is fixed, it cannot be changed until the components are replaced. Therefore, a constant speed can only be maintained in a certain speed band. (That is, it is possible to reach a constant speed in a certain speed band according to the gain value of the driving circuit, but in speed bands that cannot be covered by the gain value of the driving circuit, an overshoot or undershoot occurs, delaying the time needed to reach the constant speed.) Therefore, in the case of applying an analogue PLL type BLDC motor to an image scanning apparatus, the problem is that it is impossible to maintain a constant speed in various speed bands.
In addition, since the conventional analogue PLL type BLDC motor cannot maintain a constant speed in various speed bands, an overshoot or undershoot occurs in speed bands that cannot be covered by the gain value of the driving circuit, causing loud noise during operations of the image scanning apparatus, incorrect paper front-end margins, distorted paper image definition, and lengthening paper dragging distance during a both sides scanning.